Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface shown in an environment with a tablet.

FIG. 2 is a perspective view thereof;

FIG. 3 is a front view of a display screen or portion thereof with a graphical user interface shown in an environment with a monitor; and,

FIG. 4 is a perspective view thereof.

The broken lines showing the tablet in FIGS. 1 and 2, the monitor in FIGS. 3 and 4 are included for the purpose of illustrating environmental structure; the broken rectanble within the tablet or monitor showing the display screen and all other broken lines showing portions of the graphical user interface in all FIGS. are included for the purpose of illustrating portions of the article; all broken lines form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 